The invention relates to a 12-speed transmission for utility vehicles in 2xc3x973xc3x972.
Such transmissions usually have a pneumatically actuated front-mounted or split section, a 3-speed main gear and a pneumatically actuated rear-mounted or range section. For the main gear, a shifting device is provided which has shift rails on which shift levers are assembled which access synchronization blocks between the individual gear steps of the main gear. The shifting device is often analogous to shifting devices of 16-speed transmissions whereby an unfavorable gear shift diagram results in which the gears are not continuously shifted by a single stroke in alternating shifting directions, but on the contrary there remains, in the gear shift diagram of the course of the six gears to be shifted, a blank lying between the second and fifth gears. After the third gear, the shift lever is not passed in one stroke precisely to the fourth gear, but again must be drawn through the idling speed position in the same direction as the third gear. Only then can the fifth gear be shifted from the fourth gear in one stroke.
The problem on which the invention is based is to modify a 12-speed transmission for utility vehicles so that a shift of the main gear is possible in one stroke.
Accordingly, each shift lever otherwise actuated by the shift rail and which engages in the synchronization block of the transmission is replaced by a universal joint connection consisting of a shift fork and a reversing lever wherein the shift fork is supported fixed to the housing and shift fork and reversing lever are each actuated by their own shift rail. An engagement in the synchronization block, via a reversing lever, occurs when actuating the reversing lever in the same direction, when actuating the shift fork an opposite direction. The synchronization blocks of the transmission are then actuated either with the reversing lever or with the shift fork so that it becomes possible completely to shift the transmission in one stroke.
In such a design of the 12-speed transmission, optionally more than two gears can be shifted, via a shift rail, e.g. gears 4, 5 and 6. Thereby the shift rail engages in both synchronization blocks of the main gear. In order not to shift two gears simultaneously, the support points of the reversing lever are changed. In this case, the lever, not supported at the time, performs an idle movement. The support points are either mechanically or mechanically/pneumatically installed, according to the rotary shaft position, the support points being installed without force. Based on the chosen systematics of the shifting operation of the transmission, the support points are already brought to their place prior to the supporting operation so that no force is needed for this. Only when withdrawing the support points when shifting some gears is a very slight disengaging force required.
Consisting of a shift fork and reversing lever pivotally supported thereon, the selected construction of the individual shift levers makes different constructions of the transmission possible. Between the first and second gears, the transmission thus can have the same as, between the second and third gears, a respective synchronization block in which the shift fork or the reversing lever engage. A complete shift of the transmission in one stroke is also possible in a construction having synchronization blocks between the first and the reverse gear, the same as between the second and third gears. This is possible by implementing a reversal of the shifting device of the upper section of the transmission by the shift forks combined with reversing levers.